The objectives of this work are to develop new methods in organic synthesis from the reactions of labile systems. In particular, we are interested in applying the chemistry of cyclopropanones to the preparation of compounds of biological interest. Cyclopropanones have long been overlooked as useful reactants in organic chemistry because of the difficulties in isolating them as stable compounds. We have found, however, that cyclopropanones may be readily generated in reaction media from a variety of labile carbonyl derivatives such as hemiacetals, animals, carbinol amines and l-acyloxycyclopropanols. These precursors, a variety of which have now been isolated and purified, provide convenient sources of the parent ketones in situ and permit new explorations of their use in synthesis. One area which we have chosen specifically for study involves the ring expansion of cyclopropanones to cyclobutanones and to Beta-lactams. The facile formation of B-lactams offers an attractive route to the ring systems present in the penicillins and cephalosporins, and in our further work, we plan to explore this ring-enlargement pathway. In connection with our studies on the formation of lactams related to penicillin we also plan to investigate new routes to alpha-keto-gamma-lactams which may be ring-contracted to the penam or cepham skeleton either by oxidative cleavage, or by photochemical elimination of carbon monoxide. Other reactions in the penicillin-cephalosporin field will be studied as they offer opportunities to develop novel transformations useful in the synthesis of these antibotics and their derivatives.